Fidelity and Processivity of Saccharomyces cerevisiae DNA Polymerase η*

The yeast RAD30 gene functions in error-free replication of UV-damaged DNA, and RAD30 encodes a DNA polymerase, pol η, that has the ability to efficiently and correctly replicate past a cis-syn-thymine-thymine dimer in template DNA. To better understand the role of pol η in damage bypass, we examined its fidelity and processivity on nondamaged DNA templates. Steady-state kinetic analyses of deoxynucleotide incorporation indicate that pol η has a low fidelity, misincorporating deoxynucleotides with a frequency of about 10−2 to 10−3. Also pol η has a low processivity, incorporating only a few nucleotides before dissociating. We suggest that pol η's low fidelity reflects a flexibility in its active site rendering it more tolerant of DNA damage, while its low processivity limits its activity to reduce errors.

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